Electromagnetically operated valve

ABSTRACT

The electromagnetically operable valve has the an axially moveable valve needle which is formed from an armature, a valve-closure member and a connecting part connecting the two parts. The tubular connecting part has an elongated slit which, because of widenings of the starting sheet-metal part, has a smaller opening width at the end facing the valve-closure member than over its remaining axial extension. Thus, the valve-closure member can be attached very securely at the lower end of the connecting part by a welded seam, avoiding disadvantageous sink marks. The valve is suitable to be used in fuel-injection.

BACKGROUND INFORMATION

German Patent Application 38 31 196 describes an electromagneticallyoperable valve which has a valve needle that is axially moveable in athrough-hole of a valve-seat support. The valve needle is formed of acylindrical armature, a spherical valve-closure member and a tubular orsleeve-shaped connecting part connecting both structural elements to oneanother. The connecting part is produced from a flat sheet metal whichis subsequently rolled or bent until it assumes a cylindrical,sleeve-like shape. In this form, the connecting part has a slitextending over its entire axial length which can run eitheraxially-parallel or at an angle to the longitudinal valve axis. The twoend faces of the sheet metals used, running in the longitudinaldirection, lie opposite each other with a constant clearance forming theslit between them. When producing a fixed joining between the connectingpart and the valve-closure member by applying a welded seam using alaser (continuous wave laser), disadvantageous sink marks develop at therelatively broad slit. In this context, a sink mark is an area at whichless material is available for fusing, and at which materialconsequently falls inwardly. As a consequence, at such a location thewelded seam has a dent-shaped, concave depression which represents acertain disturbance of the welded seam. Although the laser ray is notmasked out when sweeping over the slit, the welded seam may even have abreak in the area of the slit.

German Patent Application No. 40 08 675 described an electromagneticallyoperable valve, in which the valve-closure member is attached to theconnecting part by a welded seam, the welded seam being interrupted atleast in the area of the longitudinal slit, or even additionally atfurther spots in the circumferential direction.

SUMMARY OF THE INVENTION

The electromagnetically operable valve of the present invention has theadvantage that it can be produced cost-effectively in a particularlysimple manner. It yields the advantage of a connecting part havingrelatively great tolerances. With low weight and great stability, theconnecting part has a large-area hydraulic flow cross-section. Becauseof the slit extending over the entire axial length, the connecting parthas elasticity, thus facilitating the connections to the armature andthe valve-closure member. The springy flexibility permits the connectingpart to be inserted under tension into the inner opening of thearmature, thus avoiding a disadvantageous formation of a cutting whenmounting the armature. On the other hand, the valve-closure member canbe secured very easily and reliably at the end of the connecting partfacing away from the armature, since the slit has a markedly reducedopening width. When using a continuous laser weld (continuous wavelaser) to secure the valve-closure member to the connecting part, awelded seam is advantageously attained which has no substantial break.Reducing the width of the slit at one end of the connecting part resultsin an increase of the welded cross-section and almost to an avoidance ofsink marks of the welded seam at the slit edges. The slit of theconnecting part, produced from a non-magnetic material, prevents theformation of an unwanted eddy current.

It is also advantageous to produce the connecting part from a sheetmetal, in that sheet-metal sections are first punched out in asubstantially rectangular shape and subsequently rolled or bent. Therespective elongated end faces of the sheet-metal section lie oppositeeach other with a small clearance, thus forming the slit of theconnecting part.

The fixed joining of the valve-closure member which, for example, isspherical, to the end of the connecting part, formed with a tapering ofthe slit, is attainable by a welded seam running completely around by360°, which has a very high dynamic strength.

At the lower end of the connecting part facing the valve-closure member,at the periphery exactly opposite the slit, it is advantageous toprovide a notch which ensures a reliable scavenging of the valve needle.The notch is advantageously drop-shaped, a very small opening widthexisting directly at the lower end face of the connecting part. Thus,the danger of a break in the welded seam is markedly reduced. However,sink marks of the welded seam at the notch would not be critical, sincethe dynamic stress is very much less than at the slit running over theentire axial length of the connecting part.

It is also advantageous to provide the wall of the connecting part witha plurality of flow orifices penetrating it, in order to prevent theflow conditions in the valve from undesirably influencing the ejectedfuel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial view of an electromagnetically operable valveaccording to the present invention.

FIG. 2 shows a sheet-metal section for forming a connecting part of anaxially moveable valve needle.

FIG. 3 shows a connecting part as an individual component.

DETAILED DESCRIPTION

FIG. 1 shows a partial view of an exemplary embodiment of anelectromagnetically operable valve in the form of an injection valve forfuel-injection systems of mixture-compressing internal combustionengines having externally supplied ignition. The valve has a tubularvalve-seat support 1, in which is formed a longitudinal bore hole 3concentric to a longitudinal valve axis 2. An axially moveable valveneedle 6 is arranged in longitudinal bore hole 3.

The valve is actuated electromagnetically in a conventional manner. Anelectromagnetic circuit, shown only partially, having a solenoid coil10, a core 11 and an armature 12, is used for the axial movement ofvalve needle 6, and thus for opening the valve against the springtension of a return spring 8 and for closing the valve. Valve needle 6is formed by armature 12, a for example spherical valve-closure member13 and a connecting part 14 joining the two individual parts, connectingpart 14 having a tubular shape. Return spring 8 is braced with its lowerend against the upper end face of connecting part 14. Armature 12 isjoined by a welded seam 15 to the end of connecting part 14 facing awayfrom valve-closure member 13 and is aligned with core 11. On the otherhand, valve-closure member 13 is also securely joined to the end ofconnecting part 14 facing away from armature 12 by, for example, awelded seam 16. Solenoid coil 10 surrounds core 11 which represents theend, surrounded by solenoid coil 10, of a fuel intake nipple that is notfurther described and is used for feeding the medium, in this case fuel,to be metered in by the valve.

Concentric to longitudinal valve axis 2, a tubular, metallicintermediate part 19 is tightly (e.g., imperviously) joined to the lowerend of core 11 and to valve-seat support 1 by, e.g. welding. In thedownstream end of valve-seat support 1, facing away from core 11, acylindrical valve-seat member 25 is imperviously mounted by welding inlongitudinal bore hole 3 running concentrically to longitudinal valveaxis 2. Valve-seat member 25 has a fixed valve seat 26 facing core 11.

Solenoid coil 10 is surrounded at least partially in the circumferentialdirection by at least one conductive element 30, formed, e.g. as a clipand used as a ferromagnetic element, which abuts with its one endagainst core 11, and with its other end against valve-seat support 1,and is joined to them by, for example, welding, soldering or an adhesiveconnection.

Used for guiding valve-closure member 13 during the axial movement is aguide opening 31 of valve-seat member 25. At its one lower end face 32facing away from valve-closure member 13, valve-seat member 25 isconcentrically and firmly joined to a, for example, pot-shaped aperturedspray disk 34. Valve-seat member 25 and apertured spray disk 34 arejoined, for example, by a circumferential, impervious welded seam 45formed, e.g. by a laser. This type of assembly prevents the danger of anunwanted deformation of apertured spray disk 34 in the region of its atleast one, for example four spray orifices 46 formed by eroding orpunching.

The insertion depth of the valve-seat part, composed of valve-seatmember 25 and apertured spray disk 34, into longitudinal bore hole 3determines, among other things, the adjustment of the stroke of valveneedle 6, since the one end position of valve needle 6, when solenoidcoil 10 is not excited, is established by the contact of valve-closuremember 13 against the surface of valve seat 26 of valve-seat member 25.The other end position of valve needle 6, when solenoid coil 10 isexcited, is established by the contact of an upper end face 22 ofarmature 12 against a lower end face 35 of core 11. The path betweenthese two end positions of valve needle 6 represents the stroke.

Spherical valve-closure member 13 interacts with the area of valve seat26 of the valve-seat member 25 that tapers in a frustoconical manner inthe direction of flow and is formed downstream of guide opening 31 ofvalve-seat member 25. Guide opening 31 has at least one flow passage 27which permits flow of the medium in the direction toward valve seat 26of valve-seat member 25. On the other hand, flow passages in the form ofgrooves or flattenings can also be provided on valve-closure member 13.

FIG. 3 shows connecting part 14, according to the present invention, ofvalve needle 6, as an individual component before being firmly joined toarmature 12 and valve-closure member 13, and FIG. 2 shows a sheet-metalsection 50 from which connecting part 14 can be produced. For example, achamfer 48 is formed in the shape of a ring at the upstream end ofconnecting part 14. Provided in the wall of tubular or sleeve-shapedconnecting part 14 is an elongated slit 51, completely radiallypenetrating the wall, which extends over the entire length of connectingpart 14, but at the same time has at least two axially running regionsof different slit breadth or width in the circumferential direction ofconnecting part 14.

The fuel flowing from core 11 into an inner longitudinal opening 52travels through slit 51 outwardly into longitudinal bore hole 3 ofvalve-seat support 1. Via flow passages 27 in valve-seat member 25 or atthe periphery of valve-closure member 13, the fuel arrives at valve seat26 and spray orifices 46 provided downstream, via which it is ejectedinto an induction pipe or a cylinder of an internal combustion engine.Slit 51 represents a large-area hydraulic flow cross-section, via whichthe fuel can arrive very quickly from inner longitudinal opening 52 intolongitudinal bore hole 3. The thin-walled connecting part 14 ensures thegreatest stability, accompanied by the lowest weight.

To prevent the fuel, which may be flowing asymmetrically toward valveseat 26, from undesirably influencing the jet shape of the fuel ejectedout of spray orifices 46, connecting part 14 is optionally provided witha plurality of flow orifices 55 which penetrate the wall of connectingpart 14. The, for example, circular flow orifices 55, already introducedinto sheet-metal section 50 by punching, are shown by way of exampleonly in sheet-metal section 50 of FIG. 2 and on connecting part 14 inFIG. 3. For example, twelve flow orifices 55 are arranged in alternatingrows of two and three in sheet-metal section 50. Changes with respect tonumber and position of flow orifices 55 can be implemented withoutdifficulty.

Connecting part 14 is manufactured, such that sheet-metal sections 50,similar to the one shown in FIG. 2, having a substantially rectangularshape, are produced, for example, by punching from a flat sheet metalhaving the thickness of the tubular wall of connecting part 14.Sheet-metal sections 50 have a longer and a shorter extension, thelonger extension corresponding to the length in the axial direction ofconnecting part 14 to be produced, and the shorter extensioncorresponding roughly to the circumference of connecting part 14 to beproduced. At their one end 56, to which valve-closure member 13 is latersecured, sheet-metal sections 50 have, on their two longitudinal sides,symmetrical widenings or enlargements 57 jutting out minimally beyondthe otherwise rectangular contour.

After sheet-metal sections 50 are punched out with the contour describedabove, each sheet-metal section is rolled or bent into the shape of thedesired connecting part 14, for instance with the aid of a mandrel. Inso doing, the respective elongated end faces of sheet-metal section 50forming connecting part 14 form slit 51, in that they lie opposite oneanother with a small clearance. While the width of slit 51 in thecircumferential direction is, for example, approximately 0.5 mm over thegreatest part of its longitudinal extension, in the region of widenings57, a slit region 58 results having a reduction in width of the slit toapproximately 0.1 mm.

At lower end 56 of sheet-metal section 50, a notch 59 is optionallyprovided which, for example, is arranged in such a way that at theperiphery of rolled connecting part 14, it is exactly opposite slit 51.The, for example, drop-shaped notch 59 has only a small opening width atlower end face 60, but at a distance from end face 60, is broader,wider, or more bulbous. Contours (bulb-shaped, balloon-shaped, reverseU-shape) of notch 59 differing from the contour shown in FIG. 2 areequally conceivable. Notch 59 prevents a blind hole from developing inconnecting part 14 after valve-closure member 13 is welded on, due tothe very narrow slit 51 in slit region 58 at lower end 56. Thus,reliable scavenging of valve needle 6 is completely ensured.

Producing connecting part 14 from a sheet-metal section 50 represents aparticularly light and simple type of production which permits the useof different materials and allows mass production in large quantities.The provision of slit 51 in connecting part 14 makes it elastic, so thatit is possible to select relatively rough tolerances for the inneropening of armature 12 and for connecting part 14 itself. Because of theelastic flexibility, connecting part 14 can be inserted under tensioninto the inner opening of armature 12.

Due to the very small opening width of slit 51 in slit region 58 at end56, and the optionally provided notch 59 at end face 60, and connectingpart 14 consequently abuts practically all-around against valve-closuremember 13, welded seam 16 is attainable with a very high dynamicstrength. Welded seam 16 between connecting part 14 and valve-closuremember 13 is produced, for example, which the aid of a "continuous wavelaser." In so doing, valve needle 6 is rotated under the continuouslaser ray and is continuously welded. Because of the perceptiblereduction of slit 51, the welded cross-section is enlarged compared toknown slitted valve-needle sleeves, and the sink marks of the weldedseam at the slit edges are markedly reduced to the point of almostcomplete avoidance, such that a continuous welded seam 16 exists whichis substantially disturbance-free. In addition, the dynamic stress inthe region of notch 59 is less by far than for a slit running over theentire length of connecting part 14, so that a minimal break in weldedseam 16 possibly occurring at notch 59 would not be critical.

What is claimed is:
 1. An electromagnetically operable valve having alongitudinal valve axis, comprising:a core; a solenoid coil at leastpartially surrounding the core; a valve seat; a valve-closure membercooperating with the valve seat; an armature; and a tubular connectingpart connecting the armature to the valve-closure member, the tubularconnecting part including a wall and a slit which penetrates the wall,the slit extending for an entire axial length of the tubular connectingpart from an end portion of the wall and along a remaining portion ofthe wall, the end portion facing the valve-closure member, wherein theslit has a first opening width at the end portion and a second openingwidth along the remaining portion, the first opening width being smallerthan the second opening width.
 2. The electromagnetically operable valveaccording to claim 1, wherein the tubular connecting part is formed froma sheet metal.
 3. The electromagnetically operable valve according toclaim 1, wherein the first opening width is approximately 20% of thesecond opening width.
 4. The electromagnetically operable valveaccording to claim 1, wherein the tubular connecting part includes atleast one flow orifice which penetrates the wall.
 5. Theelectromagnetically operable valve according to claim 1, wherein thetubular connecting part includes a notch which is open toward a lowerend face of the tubular connecting part, the notch being disposed at theend portion and on a periphery of the tubular connecting part which isprovided exactly opposite to the slit.
 6. The electromagneticallyoperable valve according to claim 5, wherein the notch has a drop-shape,and wherein the first opening width tapers toward the lower end face. 7.The electromagnetically operable valve according to claim 6, wherein thetubular connecting part is formed by:punching the sheet metal, andsubsequently, one of rolling and bending the sheet metal.
 8. Theelectromagnetically operable valve according to claim 7,wherein thesheet metal includes a sheet-metal section which is punched out from thesheet metal for producing the tubular connecting part, the sheet-metalsection having a substantially rectangular shape, and wherein an endsection of the sheet-metal section corresponds to the end portion, theend section including slightly protruding widened sections atlongitudinal sides of the end section.
 9. The electromagneticallyoperable valve according to claim 1, wherein the electromagneticallyoperable valve is a fuel-injection valve for a fuel-injection system ofa mixture-compressing internal combustion engine with an externallysupplied ignition.